In various mobile networks, downlink and uplink transmissions may be organized into one of two duplex modes. The two duplex modes are frequency division duplex (FDD) mode and time division duplex (TDD) mode. The FDD mode uses a paired spectrum to separate the uplink (UL) and downlink (DL) transmissions. The TDD mode, on the other hand, uses a common spectrum and relies on time multiplexing to separate uplink and downlink transmissions.
With frequency division duplex systems, assuming that neighboring cells are time synchronized, interference caused by the neighboring cells can be seen in the downlink as evolved node B (eNB) to user equipment (UE) inter-cell interference in subframes designated for downlink transmissions or in the uplink as UE-to-eNB inter-cell interference in subframes designated for uplink transmissions. Thus, the interference is created by a neighboring eNB during downlink subframes or a UE in a neighboring cell in uplink subframes.
Conversely, in TDD systems, neighboring cells may not have the same TDD configuration. In this case, there are instances where an uplink subframe on a first network occurs at the same time as a downlink subframe in a second network. In this case, there may be eNB inter-cell interference in subframes designated for opposition downlink/uplink transmissions across cells. Further, there also may be UE-to-UE inter-cell interference in subframes designated for opposite downlink/uplink transmissions across cells. Such interference may degrade system performance, especially near cell edges.